Optical-electrical hybrid module

ABSTRACT

There is provided an optical-electrical hybrid module including a substrate on which a plurality of optical communication modules are arranged, the plurality of optical communication modules transmitting or receiving an optical signal through an optical fiber cable and performing conversion between the optical signal and an electrical signal. A shield case covering the optical communication modules includes a surface inclined in a direction away from a position in which the optical fiber cable is mounted to each optical communication module.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 15/341,604, filed Nov. 2, 2016, which issued asU.S. Pat. No. 9,995,893 on Jun. 12, 2018, which is a ContinuationApplication of U.S. application Ser. No. 14/591,197, filed Jan. 7, 2015and issued as U.S. Pat. No. 9,500,822 on Nov. 22, 2016, which is aContinuation Application of U.S. application Ser. No. 13/926,346, filedJun. 25, 2013 and issued as U.S. Pat. No. 8,950,950 on Feb. 10, 2015,and which claims priority from Japanese Priority ApplicationJP-2012-177010, filed in the Japan Patent Office on Aug. 9, 2012, theentire contents of which are hereby incorporated by reference in theirentirety.

BACKGROUND

The present technology relates to an optical-electrical hybrid module,and more particularly, to an optical-electrical hybrid module intendedto realize miniaturization and high density while suppressing loss in adevice in which an optical fiber is used.

In recent years, in various electronic devices, as an amount ofinformation to be dealt with has been increasing, so has use of anoptical fiber as an information transmission channel.

In this case, for example, one end of the optical fiber is connected toan information processing device via a light transmission module. Thislight transmission module converts an electrical signal output from theinformation processing device into an optical signal and emits theoptical signal to the optical fiber. Further, a light reception moduleis connected to the other end of this optical fiber. This lightreception module converts the optical signal propagating through theoptical fiber into an electrical signal.

Further, the increasing amount of information to be dealt with hasnecessitated higher speed information communication.

For example, it is necessary to install a light transmission module or alight reception module as a high-density array for miniaturization inorder to achieve high-speed information communication in a supercomputer, a data center, or the like.

Further, the number of parts tends to increase due to the high-densityarray, and an amount of heat generated during operation of an electronicdevice increases correspondingly. Therefore, it is important to obtainsufficient shield effects and take sufficient heat radiation measures.

Technology intended to sufficiently obtain both a shield effect and acooling effect in a shield structure for a chip part has been proposed(e.g., see Japanese Patent Laid-Open No. 2004-71658).

SUMMARY

However, when a light transmission module or a light reception module ismounted at high density, it is necessary to extend an optical fiber in adesired direction while avoiding adjacent modules. Therefore, when thelight transmission module or the light reception module is mounted athigh density, it is necessary to sharply bend the optical fiber, and aloss in the optical fiber occurs at sharp bends.

When a bend radius of the optical fiber increases and the optical fiberis gently bent, the loss does not occur. However, since a distancebetween the modules increases by doing so, it is difficult for themodules to be a high-density array and it is detrimental tominiaturization.

The present technology has been made in view of such circumstances andis intended to realize miniaturization and high density whilesuppressing loss in a device in which an optical fiber is used.

According to an embodiment of the present disclosure, there is providedan optical-electrical hybrid module including a substrate on which aplurality of optical communication modules are arranged, the pluralityof optical communication modules transmitting or receiving an opticalsignal through an optical fiber cable and performing conversion betweenthe optical signal and an electrical signal. A shield case covering theoptical communication modules includes a surface inclined in a directionaway from a position in which the optical fiber cable is mounted to eachoptical communication module.

A top surface of the shield case may include a horizontal surface havinga first height determined according to a thickness of a part having agreatest thickness among parts mounted on wiring substrates of theoptical communication modules, and a horizontal surface having a secondheight determined according to a thickness of a part having a smallestthickness among the parts mounted on the wiring substrates of theoptical communication modules.

In the top surface of the shield case, the horizontal surface having thesecond height may extend by 2 mm to 15 mm long in a direction in whichthe optical fiber cable extends.

A difference between the first height and the second height may be 0.2mm or more.

A part having a greatest thickness among parts mounted on the wiringsubstrates of the optical communication modules may be a siliconinterposer.

The shield case may be formed of a metal material.

In one aspect of the present technology, an optical signal istransmitted or received through an optical fiber cable, a plurality ofoptical communication modules that perform conversion between theoptical signal and an electrical signal are arranged, and a shield casecovering the optical communication modules includes a surface inclinedin a direction away from a position in which the optical fiber cable ismounted to the optical communication module.

According to embodiments of the present technology, it is possible torealize miniaturization and high density while suppressing loss in anapparatus in which an optical fiber is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example configuration of anoptical-electrical hybrid module in which optical communication modulesof the related art are installed as a high-density array;

FIG. 2 is a graph illustrating a relationship between a bend radius andoptical loss of an optical fiber;

FIG. 3 is a diagram illustrating an example of the optical communicationmodules shown in FIG. 1 installed on a substrate in consideration of abend radius;

FIG. 4 is a diagram illustrating an example configuration of an opticalcommunication module according to an embodiment of the presenttechnology.

FIG. 5 illustrates an example configuration of an optical-electricalhybrid module in which optical communication modules according to theembodiment of the present technology are installed as a high-densityarray; and

FIG. 6 is a diagram illustrating an example configuration of an opticalcommunication module according to another embodiment of the presenttechnology.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the appended drawings, structural elementsthat have substantially the same function and structure are denoted withthe same reference numerals, and repeated explanation of thesestructural elements is omitted.

In recent years, in various electronic devices, use of an optical fiberas an information transmission channel has been increasing along withthe amount of information to be dealt with.

In this case, for example, one end of the optical fiber is connected toan information processing device via a light transmission module. Thislight transmission module converts an electrical signal output from theinformation processing device into an optical signal and emits theoptical signal to the optical fiber. Further, a light reception moduleis connected to the other end of this optical fiber. This lightreception module converts the optical signal propagating through theoptical cable into an electrical signal.

The light transmission module and the light reception module arecollectively referred to as an optical communication module. Usually, aplurality of optical communication modules are arranged on a substratein which electrical wiring patterns or the like are provided in advance,configured as an optical-electrical hybrid module, and are incorporatedinto various computers or the like.

Further, a surface of the optical communication module is covered by ashield case to protect the optical communication module from heatgenerated during operation of a device such as a computer.

Further, the increasing amount of information to be dealt with hasnecessitated higher speed information communication.

For example, it is necessary to install optical communication modules asa high-density array and miniaturize an optical-electrical hybrid modulein order to achieve high-speed information communication in a supercomputer, a data center or the like.

However, when the optical communication modules are installed at highdensity, it is necessary to extend an optical fiber in a desireddirection while avoiding the adjacent modules. Therefore, when theoptical communication modules are mounted at high density, it isnecessary to sharply bend the optical fiber, and optical loss occurs atsharp bends.

FIG. 1 illustrates an example configuration of an optical-electricalhybrid module 1 in which optical communication modules of the relatedart are installed as a high-density array. In the example of FIG. 1, anoptical communication module 20-1 to an optical communication module20-3 are installed on a substrate 10.

In FIG. 1, a distance between the adjacent optical communication modulesis d. In other words, the optical communication module 20-1 and theoptical communication module 20-2 are installed the distance d apart,and the optical communication module 20-2 and the optical communicationmodule 20-3 are also installed the distance d apart.

Further, the optical communication module 20-1 is configured in such amanner that a printed circuit substrate 22-1, a silicon interposer 23-1and the like are covered with a shield case 21-1. The opticalcommunication module 20-2 and the optical communication module 20-3 arealso configured like the optical communication module 20-1.

Further, FIG. 1 is drawn to show the inside of the shield case 21-1 forconvenience. For example, the sides or the like of the shield case 21-1are not drawn.

An optical fiber cable 31-1 to an optical fiber cable 31-3 connected tothe optical communication module 20-1 to the optical communicationmodule 20-3, respectively, extend toward a connector 40 arranged on theleft side of FIG. 1.

For example, the optical fiber cable 31-1 extends to the left in FIG. 1while avoiding the optical communication module 20-2 and the opticalcommunication module 20-3. Therefore, the optical fiber cable 31-1 issharply bent upward at a position indicated by an arrow 51-1 and to theleft at a position indicated by an arrow 51-2 in FIG. 1.

Further, for example, the optical fiber cable 31-2 extends to the leftin FIG. 1 while avoiding the optical communication module 20-3.Therefore, the optical fiber cable 31-2 is sharply bent upward at aposition indicated by an arrow 52-1 and to the left at a positionindicated by an arrow 52-2 in FIG. 1.

When the optical fiber cable is sharply bent in this way, optical lossoccurs at the sharp bends.

FIG. 2 is a graph illustrating a relationship between a bend radius andoptical loss in the optical fiber. In FIG. 2, a horizontal axisindicates the bend radius of the optical fiber, and a vertical axisindicates optical loss. The relationship between the bend radius and theoptical loss is shown by a line 61.

Further, here, the relationship between the bend radius and the opticalloss in the optical fiber at a wavelength λ=850 nm of light incident onthe optical fiber is shown.

The line 61 sharply rises from a position in which the bend radius is 20mm or less, as shown in FIG. 2. In other words, it is desirable todesign the optical-electrical hybrid module so that the bend radius ofthe optical fiber cable is equal to or more than 20 mm in order tosuppress the optical loss in the optical fiber.

However, the optical communication module is usually configured as anextremely small part having a size of 1 cm or less.

FIG. 3 is a diagram illustrating an example in which the opticalcommunication module 20-1 to the optical communication module 20-3 shownin FIG. 1 are installed on the substrate 10 so that the bend radius ofthe optical fiber cable is 20 mm or more.

In the case of FIG. 3, there is no portion in which the optical fibercable 31-1 and the optical fiber cable 31-2 are sharply bent, unlike thecase of FIG. 1. However, in the case of FIG. 3, the distance between theadjacent optical communication modules is greater than that in the caseof FIG. 1.

In other words, in the case of FIG. 3, the distance between the adjacentoptical communication modules is d′, which is greater than d. In otherwords, the optical communication module 20-1 and the opticalcommunication module 20-2 are installed the distance d′ apart, and theoptical communication module 20-2 and the optical communication module20-3 are installed the distance d′ apart.

When the adjacent optical communication modules are arranged a largedistance apart as in FIG. 3, the optical loss in the optical fiber canbe suppressed, but it is difficult to install, at high density, theoptical communication modules configured as extremely small parts. Inother words, in the related art, it is difficult to install the opticalcommunication modules at high density while suppressing the optical lossin the optical fiber.

Therefore, the present technology is intended to install the opticalcommunication modules at high density while suppressing the optical lossin the optical fiber.

FIG. 4 is a diagram illustrating an example configuration of an opticalcommunication module according to an embodiment of the presenttechnology.

A printed wiring substrate 122 is provided in an optical communicationmodule 120 shown in FIG. 4. The printed wiring substrate 122 is asubstrate in which electrical wiring patterns or the like have beenprinted in advance, and various parts are mounted on and beneath theprinted wiring substrate 122 in FIG. 4. A silicon interposer 123, aLDD/TIA 125, and a chip part 126 are mounted on the printed wiringsubstrate 122. Further, a VCSEL/PD 124 is attached to the siliconinterposer 123.

The VCSEL (Vertical Cavity Surface Emitting LASER)/PD 124 is an opticalelement that irradiates an optical fiber cable 131 with a laser beam andconverts an incident laser beam into an electrical signal. The LDD(Laser Diode Driver)/TIA (Trans Impedance Amplifier) 125 functions as adriver that drives the VCSEL/PD 124 or an IC for amplifying a weaksignal.

Further, in the optical communication module 120 shown in FIG. 4, ashield case 121 is provided to cover various parts mounted on theprinted wiring substrate 122. It is preferable for the shield case 121to be formed of a metal. Further, FIG. 4 is drawn to show the inside ofthe shield case 121 for convenience. For example, the sides or the likeof the shield case 121 are not drawn. A socket 128 is provided in a leftend in FIG. 4 of the shield case 121, and the optical fiber cable 131extends at the left side in FIG. 4 via the socket 128.

In the example of FIG. 4, an area configured as a horizontal surface ata height h1 from the printed wiring substrate 122, an area configured asa horizontal surface at a height h2 from the printed wiring substrate122, and an area inclined from the height h1 to the height h2 areincluded in a top surface of the shield case 121 (an upper surface inFIG. 4).

In other words, the top surface of the shield case 121 is configured asthe horizontal surface at the height h1 from the printed wiringsubstrate 122 in an area 121 a corresponding to a length w3 in ahorizontal direction in FIG. 4 from the socket 128. Further, the topsurface of the shield case 121 is configured as a surface inclined fromthe height h1 to the height h2 in an area 121 b corresponding to alength w2 on the right side in FIG. 4 of the above-described area 121 a.Furthermore, the top surface of the shield case 121 is configured as ahorizontal surface at the height h2 from the printed wiring substrate122 in an area 121 c corresponding to a length w1 on the right side inFIG. 4 of the above-described area 121 b.

Here, the height h1 is a height determined to correspond to a thicknessof the silicon interposer 123, which is a part having a greatestthickness in a vertical direction in FIG. 4 on the printed wiringsubstrate 122. The height h1 is usually approximately 0.8 mm to 0.2 mm.

Further, the height h2 is a height determined to correspond to athickness of the chip part 126, which is a part having a smallestthickness in the vertical direction in FIG. 4 on the printed wiringsubstrate 122. The height h2 is usually approximately 0.2 mm to 0.6 mm.

Further, the height h3 from the printed wiring substrate 122 to theoptical fiber cable 131 is a height determined to correspond to anarrangement position or a shape of the socket 128.

The top surface of the shield case of the optical communication moduleof the related art is configured as a horizontal surface at the heighth1 from the printed wiring substrate 122 over the entire printed wiringsubstrate 122. In other words, the top surface of the shield case of therelated art is configured as a horizontal surface at a uniform heightcorresponding to a height of the part having a greatest thickness in thevertical direction in FIG. 4 on the printed wiring substrate 122.

In contrast, the top surface of the shield case of the opticalcommunication module according to the embodiment of the presenttechnology has the surface inclined from the height (e.g., the heighth1) corresponding to the height of the part having the greatest verticalthickness in FIG. 4 to a lower height (e.g., the height h2) on theprinted wiring substrate 122.

Here, a distance between the adjacent optical communication modules is dand a bend radius of the optical fiber cable is r. Using the height h1,the height h3 and the bend radius r, the distance d can be derived usingEquation (1).d=(r ²−(r−(h1−h3))²)^(1/2)  (1)

For example, if (h1−h3)=1 mm, the distance d is 6.2 mm from Equation (1)when the horizontal top surface at the height h1 from the printed wiringsubstrate 122 over the entire printed wiring substrate 122 is provided,as in the shield case of the optical communication module of the relatedart. In other words, in a scheme of the related art, it was necessary toperform an arrangement with a distance between adjacent opticalcommunication modules being equal to or more than 6.2 mm.

In contrast, when the optical communication module according to theembodiment of the present technology is used as shown in FIG. 4, if(w1+w2) is 6.2 mm or more, the distance d can be approximately 0. Whenan optical communication module having a general size is configured, itis desirable for w1 to be 2 to 15 mm and (h1−h2) to be 0.2 mm or more.

FIG. 5 illustrates an example configuration of an optical-electricalhybrid module to which the present technology has been applied, which isan optical-electrical hybrid module 100 in which optical communicationmodules according to the embodiment of the present technology areinstalled as a high-density array. In the example of the FIG. 5, anoptical communication module 120-1 to an optical communication module120-3 according to the embodiment of the present technology areinstalled on a substrate 110.

An optical fiber cable 131-1 to an optical fiber cable 131-3, connectedto the optical communication module 120-1 to the optical communicationmodule 120-3, respectively, extend toward a connector 140 arranged onthe left side in FIG. 5.

For example, the optical fiber cable 131-1 extends to the left in FIG. 5while avoiding the optical communication module 120-2 and the opticalcommunication module 120-3. However, in the example of FIG. 5, there isno portion where the optical fiber cable 131-1 is sharply bent, unlikethe case described above with reference to FIG. 1. Further, the opticalfiber cable 131-2 extends to the left in FIG. 5 while avoiding theoptical communication module 120-2 and the optical communication module120-3. However, in the example of FIG. 5, there is no portion where theoptical fiber cable 132-1 is sharply bent, unlike the case describedabove with reference to FIG. 1.

Therefore, according to the embodiment of the present technology, it ispossible to suppress optical loss in the optical fiber.

Further, in FIG. 5, a distance between the adjacent opticalcommunication modules is d. In other words, the optical communicationmodule 120-1 and the optical communication module 120-2 are installedthe distance d apart, and the optical communication module 120-2 and theoptical communication module 120-3 are also installed the distance dapart. In other words, it is unnecessary for the distance between theadjacent optical communication modules to be d′, which is greater thand, unlike the case of FIG. 3.

Therefore, according to the embodiment of the present technology, it ispossible to install the optical communication modules at high density.

FIG. 6 is a diagram illustrating another configuration example of anoptical communication module according to an embodiment of the presenttechnology.

In an optical communication module 120 shown in FIG. 6, a printed wiringsubstrate 122 is provided, as in the case of FIG. 4. Further, as in thecase of FIG. 4, a silicon interposer 123, an LDD/TIA 125, and a chippart 126 are mounted on the printed wiring substrate 122. Further, aVCSEL/PD 124 is attached to the silicon interposer 123.

The optical communication module 120 shown in FIG. 6 differs from thatof FIG. 4 in a configuration of the shield case 121. Further, FIG. 6 isdrawn to show the inside of the shield case 121 for convenience. Forexample, the sides or the like of the shield case 121 are not drawn.

In the example of FIG. 6, an area configured as a horizontal surface ata height h1 from the printed wiring substrate 122, and an area inclinedfrom the height h1 to a surface of the printed wiring substrate 122, areincluded in a top surface of the shield case 121 (a top surface in FIG.6).

In other words, the top surface of the shield case 121 is configured asa horizontal surface at the height h1 from the printed wiring substrate122 in an area 121 d corresponding to a length w5 in a horizontaldirection in FIG. 6 from a socket 128. Further, the top surface of theshield case 121 is configured as a surface inclined from the height h1to the surface of the printed wiring substrate 122 in an area 121 ecorresponding to a length w4 on the right side in FIG. 6 of theabove-described area 121 d.

In the case of FIG. 6, for example, the horizontal surface correspondingto the area 121 c in the configuration of FIG. 4 is not included.

If the optical communication module 120 having the configuration shownin FIG. 6 is used, it is not necessary to sharply bend the optical fibercable 131 even when the distance between the optical communicationmodules 120 is small. Therefore, even when the configuration of FIG. 6is applied, according to the embodiment of the present technology,optical loss in the optical fiber can be suppressed and the opticalcommunication modules can be installed at high density.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

Additionally, the present technology may also be configured as below.

-   (1) An optical-electrical hybrid module including:    -   a substrate on which a plurality of optical communication        modules are arranged, the plurality of optical communication        modules transmitting or receiving an optical signal through an        optical fiber cable and performing conversion between the        optical signal and an electrical signal,    -   wherein a shield case covering the optical communication modules        includes a surface inclined in a direction away from a position        in which the optical fiber cable is mounted to each optical        communication module.-   (2) The optical-electrical hybrid module according to (1), wherein a    top surface of the shield case includes a horizontal surface having    a first height determined according to a thickness of a part having    a greatest thickness among parts mounted on wiring substrates of the    optical communication modules, and a horizontal surface having a    second height determined according to a thickness of a part having a    smallest thickness among the parts mounted on the wiring substrates    of the optical communication modules.-   (3) The optical-electrical hybrid module according to (2), wherein,    in the top surface of the shield case, the horizontal surface having    the second height extends by 2 mm to 15 mm long in a direction in    which the optical fiber cable extends.-   (4) The optical-electrical hybrid module according to (2), wherein a    difference between the first height and the second height is 0.2 mm    or more.-   (5) The optical-electrical hybrid module according to (2), wherein    the part having the greatest thickness among the parts mounted on    the wiring substrates of the optical communication modules is a    silicon interposer.-   (6) The optical-electrical hybrid module according to any one of (1)    to (5), wherein the shield case is formed of a metal material.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2012-177010 filed in theJapan Patent Office on Aug. 9, 2012, the entire content of which ishereby incorporated by reference.

What is claimed is:
 1. An optical device comprising: a wiring substrate;a shield case; and in a cross-section view, a first portion, a secondportion, and a third portion, the first portion includes a firstcomponent including a light emission element and a light detectionelement on which an optical element is attached, wherein the firstcomponent is configured to couple to at least one optical fiber, and afirst horizontal surface of the shield case that covers the firstcomponent, the second portion includes a second component mounted on thewiring substrate, and a second horizontal surface of the shield casethat covers the second component, and the third portion includes aninclined surface of the shield case between the first horizontal surfaceand the second horizontal surface, wherein a surface of the wiringsubstrate facing the first horizontal surface and the second horizontalsurface defines a first plane, wherein, in the first portion, the lightemission element and the light detection element are entirely betweenthe first horizontal surface and the first plane, and wherein a lightemission direction from the light emission element to the at least oneoptical fiber and a light reception direction from the at least oneoptical fiber to the light detection element are parallel to the firsthorizontal surface.
 2. The optical device according to claim 1, whereina top surface of the second component facing the second horizontalsurface defines a second plane, and wherein the light emission elementand the light detection element are located between the first horizontalsurface and the second plane.
 3. The optical device according to claim1, wherein the first horizontal surface defines a second plane, andwherein a socket is located between the second plane and the firstplane.
 4. The optical device according to claim 1, wherein the wiringsubstrate is a printed wiring substrate.
 5. The optical device accordingto claim 1, wherein the light emission element is a Vertical CavitySurface Emitting Laser (VCSEL) and is configured to irradiate the atleast one optical fiber.
 6. The optical device according to claim 1,wherein the third portion includes an optical driver mounted on thewiring substrate and is configured to drive the light emission element.7. The optical device according to claim 6, wherein a top surface of theoptical driver facing the inclined surface and the top surface of thesecond component define a second plane.
 8. The optical device accordingto claim 7, wherein the optical driver is between the first plane andthe second plane.
 9. The optical device according to claim 6, whereinthe optical driver is a Laser Diode Driver/Trans Impedance Amplifier(LDD/TIA).
 10. The optical device according to claim 6, wherein theoptical element is configured to receive an electrical signal from theoptical driver, and control the light emission element to emit lightbased on the electrical signal.
 11. The optical device according toclaim 1, wherein the optical element is configured to receive an opticalsignal from the at least one optical fiber, and convert the opticalsignal to a first electrical signal.
 12. The optical device according toclaim 1, wherein the shield case is a metal shield case.
 13. The opticaldevice according to claim 1, wherein the inclined surface is inclinedfrom the first horizontal surface to the second horizontal surface. 14.The optical device according to claim 1, wherein a sum of a length ofthe inclined surface and a length of the second horizontal surface is6.2 mm or more.
 15. The optical device according to claim 1, wherein alength of the second horizontal surface is a range between 2 mm and 15mm.
 16. A system comprising: a first optical device; a second opticaldevice; a first optical fiber coupled to the first optical device; asecond optical fiber extending over the first optical device and coupledto the second optical device, wherein the first optical device includesa wiring substrate; a shield case; and in a cross-section view, a firstportion, a second portion, and a third portion, the first portionincludes a first component including a light emission element and alight detection element on which an optical element is attached, whereinthe first component is configured to couple to at least the firstoptical fiber, and a first horizontal surface of the shield case thatcovers the first component, the second portion includes a secondcomponent mounted on the wiring substrate, and a second horizontalsurface of the shield case that covers the second component, and thethird portion includes an inclined surface of the shield case betweenthe first horizontal surface and the second horizontal surface, whereina surface of the wiring substrate facing the first horizontal surfaceand the second horizontal surface defines a first plane, wherein, in thefirst portion, the light emission element and the light detectionelement are entirely between the first horizontal surface and the firstplane, and wherein a light emission direction from the light emissionelement to the at least one optical fiber and a light receptiondirection from the at least one optical fiber to the light detectionelement are parallel to the first horizontal surface.
 17. The systemaccording to claim 16, wherein a distance between the first opticaldevice and the second optical device is less than 6.2 mm.
 18. The systemaccording to claim 17, wherein the distance between the first opticaldevice and the second optical device is approximately zero.
 19. Thesystem according to claim 16, wherein a sum of a length of the inclinedsurface and a length of the second horizontal surface is 6.2 mm or more.20. The system according to claim 16, wherein a length of the secondhorizontal surface is a range between 2 mm and 15 mm.
 21. The systemaccording to claim 16, wherein the second optical device includes asecond wiring substrate; a second shield case; and in a secondcross-section view, a first portion, a second portion, and a thirdportion, the first portion includes a first component mounted on thesecond wiring substrate and including a light emission element and alight detection element on which an optical element is attached, whereinthe first component is configured to couple to at least the secondoptical fiber, and a first horizontal surface of the second shield casethat covers the first component, the second portion includes a secondcomponent mounted on the second wiring substrate, and a secondhorizontal surface of the second shield case that covers the secondcomponent, and the third portion includes an inclined surface of thesecond shield case between the first horizontal surface and the secondhorizontal surface, wherein a surface of the second wiring substratefacing the first horizontal surface and the second horizontal surfacedefines a first plane, wherein, in the first portion, the light emissionelement and the light detection element are between the first horizontalsurface and the first plane, and wherein a light emission direction fromthe light emission element to the second optical fiber and a lightreception direction from the second optical fiber to the light detectionelement are parallel to the first horizontal surface.